Single-constrained QoS routing protocols have inherent defects when applied into wireless ad hoc networks. Due to a single constraint parameter is only considered, they can't always cope with the problems caused by the uncertainty of ad hoc networks well. They are not robust enough. In order to overcome the drawbacks of single-constrained QoS routing protocols and improve the Quality of Service (QoS) of ad hoc networks, this paper proposed a multi-constrained QoS routing protocol based on fuzzy logic. It is developed from Dynamic Source Routing (DSR). The proposed protocol is service-aware in the sense that it considers the QoS required by different types of services and takes different network state parameters as the constraint conditions for fuzzy based routing system. New route discovery procedure and novel route maintenance mechanism are designed to support corresponding QoS requirements. Speed of packets sending is also adjusted adaptively referring to the outputs of the proposed fuzzy system. Performance of the fuzzy based DSR protocol is measured and evaluated under different conditions. Simulation results show that the improved protocol has better QoS guarantee capabilities compared to single-constrained QoS routing protocols for large-scale networks in terms of lower delay, smoother delay variation and lower packet loss rate.
A Robust Route Maintenance Scheme for Wireless Ad-Hoc Networks
